DESCRIPTION (Applicant's abstract):Exercise capacity is reduced in patients with heart disease and hypertension limiting the therapeutic value of its prescription. The long-term goal of this proposal is to understand circulatory control during exercise mediated by intramuscular somatosensory input in chronic disease. The first objective is to develop a reproducible exercise model in which cardiovascular disease is readily induced. A decerebrate rat preparation will be used and the effect of mechanically and metabolically-sensitive hindlimb afferent activity on circulatory control will be investigated. The second objective is to characterize alterations in cardiovascular control during exercise after the development of heart failure. Myocardial infarction will be induced in rats via coronary artery ligation. Changes in heart rate, blood pressure, and renal sympathetic nerve activity will be measured in response to static muscle contraction and passive muscle stretch after decerebration. The third objective is to identify changes in circulatory regulation during exercise in hypertension using the methods presented above. A genetically engineered strain of spontaneously hypertensive rats will be employed and responses compared to a control group of normotensive rats. Results from these experiments will not only describe a novel animal preparation for the study of cardiovascular control by intramuscular neural mechanisms but will lead to an improved understanding of circulatory regulation during exercise after the manifestation of clinical pathologies.